Taper snap switch



' April 12, 1949.

File@ sept. 4.- 194s J. H. SCHELLMAN TAPER SNAP SWITCH 5 Sheets-Sheet 2 fw S j April 12, 1949. J. H. SCHELLMAN 2,466,970

TAPER SNAP SWITCH 5 Sheets-Sheet 3 Filed Sept. 4, 1945 W-@vl l v 8 IV/A Patented Apr. 12, 1949 TAPER SNAP SWITCH Joseph H. Soheilman, Ridley Park, Pa., assignor to Robert Hetherington da Son, Inc., Wilming-- ton, Del., a corporation of Delaware Application September 4, 1945, Serial No. 614,137

3 Claims. (C1. 20o-77) l My invention relates to a plunger switch of self-retracting type.

The main purpose of the invention is to shorten the total length of a plunger switch.

A further purpose is to locate the retracting spring of a plunger switch at the -rear end of the plunger and permissibly about an inverted cap guide.

A further purpose is to provide a spring-receiving cup rigid upon the front of a switch plunger to nt into the push button of a switch, the cup and hollowl button together housing an over-travel spring for the plunger;

A further purpose is to form a rearwardly facing cup on a switch plunger and enclose a retraction spring within it and within a well in the rear switch insulation.

Figure 1 is a longitudinal section of a. preferred form of the invention, showing the switch in open position.

Figure 2 is aview corresponding to Figure 1 and showing the switch in closed position.

Figures 3 and 8 are bottom plan views of the structures seen in Figures 1 and 7.

Figure 4- is a perspective view of a plunger seen in Figures 1, 2 and 7.

Figure 5 is a perspective of the rear insulation unit including one pair only of stationary contacts carried by it as illustrated in Figures 1 and 2 and intended for closure and opening of a single circuit only.

Figure 6 is a perspective view of a shorting bar or shuttle which is. used in Figures 1 and 2.

Figure 7 is a longitudinal section of a variant of the invention illustrating the switch having double sets of contacts.

Figure 9 is a section taken upon line 9-9 in Figure 7 showing the upper pair of two pairs of ilxed contacts and the shorting bar in top plan view.

Figure 10 is a bottom plan view of the shorting bar or shuttle as seen in Figure 9.

Figure 11 is a central longitudinal section of a variant form of the invention, omitting the overtravel spring.

Figure 12 is a central longitudinal section of a variant form of the invention in which the plunger is guided by the springs at each end.

Figure 13 is a perspective of the plunger seen in Figure 12.

Figures 13a and 13b are fragmentary modifications of Figure 13.

Figure 14 is a section upon line I4-I4 of Figure 13a.

Figure 15 is a sectional perspective view of the form of the invention shown in Figures 16 and 17.

Figure 16 is a central longitudinal section of a modification of the invention using a iiat plunger and ilat cams, with the switch in open position.

Figure 17 is a view .corresponding to Figure 16 with the switch shown in closed position..

Figure 18 is a section upon line |3I8 in Figure 16.

Figure 19 is a section upon line I9-I9 in Figure 17.

Figure 20 is a central longitudinal section of a variant form of the invention using a. flat plunger and iiat cams, with double sets of contacts.

Figure 21 is a section upon line 2I-2I in Figure 20.

f Figures 22 and 23 are sections at right angles to each other, corresponding to the positions of lines 22-22 and 23-23 in Figure 6, but showing a modied form seen in Figure 20.

Figure 24 is a. fragmentary vertical central section of a modiiled form.

My invention has been illustrated in forms in which the outer casing 30, 30 is connected with the rear insulation unit, 3|, 3l', and 3l2 either by friction and a pin as in Figures 1, 2, 11, 15, 16 and 17, or by threads as at 32 in Figure 7. An insulation such as plastic forms a desirable material for the casing, but metal can be used if spacing of the contacts from the casing be maintained.

The rear insulation unit preferably is flanged at 33 to engage the rear of the casing. The casing in most instances will preferably be mounted at the front end upon a switch holding panel board or other support through threads 34,

v The casing 30 and the rear insulation block 3| will carry diiferent numbers of fixed contacts according to whether a single circuit or two circuits is or are to be closed and opened and, in the flat plunger form, will carry guide grooves for wings or guides.

Taking up rst the form shown in Figures 1 to 6, the outer casing is exteriorly threaded at 34 to provide for mounting upon Va panel 35 in which it is held by nuts 39 and 40 and a lock washer 4|. The opening in the panel is also shown as threaded at 42 in this form so that there is a lock nut eiect between this thread and the threads of the nuts used. Y

The interior of the casing is bored and counterbored to provide, considered from the rear, bores 43, 44, 45 and 46 with rearwardlyA facing edge 41 and shoulders 48, 49 and 50 between the bores.

The rear insulation block 3| is preferably shouldered at 5| to engage and seal against the andere 3 rearwardly facing edge 41. It fits bore 43 and engages the shoulder 48 for the advantage of of additional sealing. y

Since a single circuit only is closed and opened in the form of Figures 1 to 6, a single pair only 52 and 53 of xed terminals is shown in these gures.

The terminals 52 and 53 are fastened within the insulation block. In the illustrations they are shown as molded within, but clearly could be put in by any method which, in connection with the surrounding casing, will`retain them rmly in position while maintaining their insulated condition. 'I'he character of the mounting of the terminals and fixed contacts within the block is not of the essence here. At their front ends the terminals are turned toward each other at 5I, 55 to form fixed contact ends. They are carried forward far enough to permit the entire switch operation Vto takeplace back of these fixed contact ends, with whose rearwardly facing sides circuit closing c'Ontact is made. Connection is made to the terminals at 56 and 51.

The block *ll` is recessed at 58 to permit the 1ocation within it of a spiral retracting spring 59.

At the front is located a push button 60 which is hollow in Figures 1 and 2 and there through a spiral overtravel spring 5I, presses a plunger 52 against the retracting pressure of the spiral spring 59, the connection between the plunger and the spring being variously shown in the different figures, in Figures 1-6 being indicated by a cup 53 within which the end 54 of the plunger rests and a ange 55 by which the cup engages the forward end of the retraction spring.

The overtravel spring 6i exerts a greater expansion pressure than the retraction spring, so that the overtravel spring is not compressed until the switch is thrown and, permissibly, the bottom 56 of the cup 53 engages the bottom 61 of the recess, or the compression of the spring acts as a stop, after which the overtravel spring compresses to permit additional movement of the push button so as to insure a full stroke or to permit reliable movement of the plunger by an operating member which is uncertain in its extent of movement.

The overtravel spring in the form of Figures 1-10 fits within a forwardly facing cup 50 integral with the outer end of the plunger, and the outside of the cup sides within the hollow of press button 60.

The push button 50 is fitted within the casing from the rear and is stopped by the shoulder 1li of the buttonflange 1i engaging the shoulder 50 of the casing.

The plunger operates a shorting bar 12, which is shown to advantage in Figure 6, and which includes an electrically conducting sheet forming the front face 13 of the shorting bar or shuttle.

The front sheet is bent down at 1I. 15 to form ends 16 of the shorting bar and ultimately form stops 11 to limit the shorting bar travel and, where two circuits4 are to be closed and opened, to engage terminals to close a circuit.

The ends of the shuttle help to house spring means within the shuttle for squeezing the plung- -er at opposite sides. In Figures 1 and 2 the spring means .used comprises two separate springs and 19, whose sides near the ends are restrained against lateral movement away from each other by inwardly turning ears 80 and 8i.

The ears spring from the rearwardly turned t ends. The extents to which these ears are turned,

i 4 as well as the size of the wire from which the springs are wound, the diameters and pitches of the springs all tend to control the resistance of the springs to displacement of the central parts of the springs laterally to positions such as are shown in Figure 9.

The rear face of the shorting bar or shuttle is preferably form by an insulating plate 82, held in place by eaggment of the inwardly turned ends 80 and Il or parts carried by them.

The front plate and the rear plate 82 (if a rear plate be used) are apertured at I4 and ll' to permit the plunger to operate through the apertures, passing between the springs 15 and.

19. The plunger carries a double cam 85 having faces 56 and 81 and crest Il. There are rests at the opposite ends of the cam faces.

The plunger passes between the transverse shorting bar springs and, as the push button is pressed rearwardly the (rear) cam face' 81 presses the springs aside so that with continued movement the crest passes between the springs, and the pressure of the springs'laterally upon the forwardly and outwardly facing (front) cam face causes the shorting bar to move forward from the position of Figure 1 to the position of Figure 2, at .which latter the shorting bar front face engages with and connects across between the two contacts 52 and 53.

It will be noted that there has been no compression of the overtravel spring, but the button and the plunger have moved rearwardly together.

With any further movement of the button rearwardly from the position of Figure 2, there will be compression of the overtravel spring lying within the button, but no further rearward movement of the plunger.

When the pressure upon the button is wholly released, the overtravel spring within the button will expand first, if it has been compressed, and the retraction spring will respond next, pressing the plunger forwardly between the springs until the crest of the double cam passes the central transverse plane between the springs, after which the contraction of the springs against the rear in a direction opposite to the direction of the movement, of the plunger and, in whichever dlrection of movement, immediately after the crest of the cam passes the central plane through the axis of the two opposing springs, or, if the springs be not separated, after the central spring plane has been passed.

In the illustrations where the rearward movement of the plunger is the switch closing movement, and the forward movement of the plunger is the switch breaking direction of the plunger movement, the rearward cam face is made steeper than the forward cam face in order that the breaking (separating) movement of the shorting bar may be more rapid than the closing movement. This has been maintained in the different gures.

The fact that the cam surfaces in the figures are unequal in length,` providing for a more rapid switch opening stroke than the switch closing stroke for the contacts made on forward-movement of the shorting bar corresponding to rearward movement of the plunger, is of general value and is of value in this case. notwithstanding that much of the present invention is wholly independent of the question of whether these cam faces be of equal or of unequal length.

In Figure 11 the structure diiers from that of Figures 1 and 2, for example, in that the overtravel spring has been omitted wholly along with its function` The forward end 62' of the plunger is fastened securely to the plunger within the button.

In Figure 12 the structure corresponds generally with Figures 1 and 2, with several differences. however. The overtravel spring BI' is larger in diameter than in Figures 1 and 2, and the outside of the spring acts as a guide with the opening in the rear of a button so that the spring will compress wlthin the button properly, without the necessity for the cup guiding walls on the outside of the spring.

The forward part 623 of the plunger assists in the guiding function by fitting within the overtravel spring, maintaining the overtravel spring in line and holding it inline during its compression within the opening in the button. Because the overtravel spring is interiorly guided, it does not need any cup guides. The cup is omitted and instead of the cup Figures 12 and 13 show a flange ring 83 to act as a springseat. Similarly, no cup is used Iat the rear of the plunger, but a ring 84 is used, rigid with the plunger.

Thus it will be evident that the form of plunger in Figures 12 .and 13 provides guiding in the spring at both ends (the button end and the insulation block end), with a difference, however, that at the button end the plunger guides that portion of the overtravel spring which lies outside the spring recess into the recess during compression, while in the rear insulation block the recess is normally of suicient depth so that it fully contains the retraction spring both when compressed and expanded.

In Figures 11 and 12 a single circuit only is closed, but this general construction can be suited to a. control of two separate circuits, one being opened when the other is closed and vice versa, as in Figure 7.

In Figures 13a, 13b and 14 to 23 structures are shown similar to the structures in the preceding figures, but using a plunger 85 of iiat cross section as distinguished from the plunger of circular cross sections shown in the preceding figure.

For reasons which chiefly concern an -attempt to make the switch as small as possible, it is very desirable to'prevent the at plunger from turning with respect to the casing and rear insulation, and also to prevent the shorting bar from turning about the at plunger.

The fiat plunger may be used with -at ears 88 for compression of an overtravel spring 81 paralleling generally the construction of Figure 12, excepting that a shorter overtravel is here used (see Figure 13a) or the at end may be forked, as at 88 (Figure 13b) following in this respect the forms generally of Figures 1, 2, and 7. In either event, whether the ears or the forked sides be used, they should be kept in the center as by the walls of grooves 89 (see Figures 13a and 14). The grooved walls can .afford lateral support in all directions for the upper ends of the plungers. The spring 81' in Figure 13b is guided laterally by the contour kof the main recess in the button.

As in the case of the plunger of circular cross section, the plunger 85' is mounted directly in the push button where the overtravel function is not desired (see Figures 15 to 171and 20).

The double cam in Figures 15, 16, 17 and 20 must be kept approximately perpendicular to the adjacent section of whatever shorting bar springs are used. It is shown in these figures and in Figure 18 as approximately perpendicular to the surfaces of the two initially parallel constrlcting springs there illustrated. This position of the edges 90, 9|, 92 and 93 is maintained in the shorting bar by the walls of a slot 94, which is long enough to take the width of the bar at the crest 95. A similar slot 96 is shown in the lower plate 91 of the shorting bar.

The shorting bar is kept from turning with respect to the rear insulation blockand hence with respect to the terminals and their contacts carried by this blockby wings 98, traveling in slots 99 and adapted to compress retraction springs |00.

In Figures 15, 16 and 17 a single circuit is intended to be closed when the parts are moved from the position of Figure 16 to the position of Figure 17. In the latter the parts are in closed circuit position and the wings 98 hold the retraction spring in compressed position.

In Figures 22 and 23 sections at right angles to each other show the guiding slot through the front and rear plates of the shorting bar, as well as the turned ends of the shorting bar which face each other in Figure 22, and which provide the shorting bar contacts by which the second set of contacts are connected to close the second circuit.

The'turned fixed facing contacts of a second circuit, such as are seen in vFigure 7, are shown in Figure 20, but are intended to be closed by straight-skirted contact-making shorting bar rear contacts of the character shown in Figures 1 and 2 for stop purposes.

It will be evident that the method of operation of the flat form, whether with or without overtravel spring provision, is substantially identical with the corresponding `mode of operation of the type whose plunger is of circular cross section with or without overtravel switch, and that the types using the flat plunger are capable of performing the same function in the same general way as those characterized by a circular plunger; also that the same general effect can be produced in compression and release of overtravel spring and retraction springs, whether a cupped plunger end of circular cross section be used, as in Figures 1 and 2, or a ringed type, see in Figures 11, 12 and 13, or a winged or forked type of flat plunger.

The fact that the shorting bar is prevented from turning with respect to the flat' plunger as well as with respect to the xed contacts to be made by it makes it possible to omit the rear insulation plate from the shorting bar in Figure 21 and to turn the ends of the shorting bar plate directly across through the space occupied in the other figures by this rear shorting bar plate. This resembles somewhat the structure seen in Figure 7, though in this latter structure a circular plunger is used and the shorting bar is not prevented from rotating.

In Figure 24 a longitudinal section is shown,

extending from the forward fixed contacts to a rearward position corresponding nearly with the rear end position of the plunger shaft in Figure 17; but the purpose of the view is to illustrate a change in the shorting bar and in the rear contacts as compared with the shorting bar in Figure 22, for example, and the rear contacts in Figure 7.

In this Figure 24 the rear (insulation) plate of the shorting bar has been omitted altogether and the downwardly turned electrically conducting ends of the shorting bar have been turned toward each other immediately adjacent the springs in the shorting bar, whose lower inturned edges close the second circuit by engaging with the inturned fixed contacts of the rear circuit. Advantage could, of course, be taken of this construction to shorten the switch, leaving the ends of the fixed contact of the second circuit where they are in Figure 7. for example, or as in Figure 24, the same length of casing, rear insulation block, etc. can be maintained by advancing the second set of terminals and their ends turned towards each other to an extension in front of the rear insulation block. corresponding generally with the thickness of the rear plate of the shorting bar.

The above form of the invention is intended to be used with the flat form of plunger shaft and flat cam seen in Figure 24 and having, if desired, an overtravel spring. In this switch the at plunger shaft and cams are guided by the slots seen in Figures 22 and 23 against rotation with respect to the snorting bar and at the rear end of the plunger shaft are kept from rotation with respect to the fixed rear insulation block by ears within grooves, as in the case of Figures 16 and 17, for example, so that short circuiting may be avoided and the sloping sides of the flat cam may be maintained in position perpendicular to the shorting bar springs with which they are to be engaged.

In operation the push button is pressed rearwardly compressing the retraction spring; and this is true whether there be an overtravel spring or not. With an overtravel spring in place, the push button can move beyond the switch position at which the retraction spring has been sumciently or wholly compressed.

In .the case of the nat plunger shaft the entire shaft is guided against turning. At the rear end of the shaft ears engage the walls of slots in the insulation and at an intermediate point the flat sides of the shaft engage the walls the slots within the forward and, usually, also the rearward slots in the shorting bar.

It makes no difference in the operation whether the plunger shaft in the circular form presses against a cup whose flanges engage the retraction spring or whether a ring or other annular projection from the shaft serves this function.

Having thus described my invention what I claim asnew and desire to secure by Letters Patent is:

l. In a plunger switch, a tubular switch casing having an interior bore and an insulation portion extending longitudinally around the bore, a rear insulation block in the casing having a forwardly facing recess at the front of the block, ilxed metallic contacts extending on either side of the recess through the block and having contact ends exposed in the bore for contact engagement, a

plunger extending longitudinally through the center of the casing into the bore between the longitudinally extending contacts, a switch button in the bore at the front of the bore operatively interconnected with the plunger, a spring in the recess compressed by rearward movement of ythe plunger, a spring abutment carried by the plunger and bringing pressure from the plunger on the end of the spring, a double cam carried by the plunger and a shorting bar surrounding the plunger, spring urged by the cam to opposite limiting position and making contact with the 8 contacts in at least one of the limiting positions.

2. In a plunger switch, a casing having an interior bore and insulation interiorly exposed around the bore, a rear insulation block in the casing having a forwardly extending recess and having guideways longitudinally extending in the walls of the recess, xed contacts on either side of the recess extending longitudinally through the block and having contact faces exposed in the bore for contact making purposes, a switch button in the bore at the forward end of the casing, a flat plunger extending longitudinally through the center of the -bore and operatively connected to the switch button, oppositely facing flat cams mounted on the plunger, a shorting bar surround. ing the plunger at the cams, spring urged on the cams longitudinally in one or the other direction and having a flat-sided slot which engages the plunger and is prevented from rotation by the flat plunger, the shorting bar engaging the contacts in at least one limiting position, a spring abutment on the rear of the plunger, a spring in the recess behind the spring abutment urging the plunger forward and projections on the plunger into the guideways of the recess preventing rotation of the plunger with respect to the casing, whereby the structure is freely movable longitudinally but is held against rotation in the case of the plunger by the guideways and in the case of the shorting bar by the plunger.

3. In a switch, a tubular casing having an interior bore and having insulation exposed along the bore, an insulation -block in the bottom of the bore having a forw-ardly presented recess and having guideways extending longitudinally of the recess, spaced contacts on either side of the recess extending longitudinally through the block and having contact ends exposed in the bore for contact making, a nat plunger extending centrally through the bore, oppositely directed cams on the plunger, a snorting bar surrounding the plunger at the cams and spring urged in one direction or the other by the cams to make contact with the contacts in at least one limiting position, a button at the forward end of the bore having an interior rearwardly facing recess, an overtravel spring in the recess of the button, a spring abutment on the plunger engaging the overtravel spring, guideways on the recess in the button extending longitudinally, projections from the plunger engaging the guideways, a retraction spring in the recess in the block, a spring abutment on the plunger engaging the retraction spring and projections from the plunger engaging the guideways in the block. y*

JOSEPH H. SCHELLMAN.

REFERENCES CITED The following references areof record in the Number Name Date 1,011,754 Cubitt Dec. 12, 1911 1,182,087 Hart May 9, 1916 1,695,359 Bath Dec. 18, 1928 1,837,185 Jones Dec. 15, 1931 2,195,764 Hill Apr. 2, 1940 2,345,240 Cox. Jr Mar. 28, 1944 2,384,412 Woods Sept. 4, l1945 2,386,162 Hetherington Oct. 2, 1945 

